Women on the Facebook Board will help improve Facebook's financial effectiveness and strategic thinking

Women on the Facebook Board will represent Facebook's largest groups of users

Women on the Facebook Board will represent Facebook's most profitable group of users

Women on the Facebook Board will demonstrate that Facebook is a progressive corporation with enlightened (as in, not sexist, not racist) assumptions about human talent, skill and value

And, women on the Facebook Board will burnish Facebook's public image, keeping the stock price high.

When it comes right down to it, if Sandberg is really to be considered a 'powerful' woman, or a real leader, she needs to demonstrate that she has power, by tackling the ultimate leadership challenge-- directing her influence upward, to get her boss(es) to do the right thing.

Sandberg herself has said that, to achieve gender equity, we need more women at the top of corporations.